Field of the Invention
The invention relates to a speed-changing and differential transmission having a housing, having an input shaft and two output shafts, disposed coaxially with the input shaft, wherein a speed-changing section and a differential section configured as a spur wheel differential are provided, wherein the speed-changing section has two planetary stages, namely an input stage and a load stage, wherein the sun wheel of the input stage is operatively connected to the input shaft, wherein the load stage has an annulus fixed in relation to the housing and the sun wheel of the load stage can be operatively connected to at least one planet wheel of the input stage through the use of a planer carrier and wherein at least one planer wheel of the load stage can be operatively connected to the annulus of the input stage through the use of a planet carrier. The invention furthermore relates to a motor and transmission unit having an electric motor and a speed-changing and differential transmission as mentioned above flanged coaxially to the electric motor.
Customary types of construction of transmissions in electric vehicles are based on conventional transmissions for coupling to internal combustion engines. These transmissions have an axial offset between the input and output shaft, i.e. between the rotor shaft of the electric motor and the wheel shafts. The flanged shafts for the wheels are routed past the prime movers (electric motor or internal combustion engine) in an appropriate manner, substantially axially parallel with the prime movers. Here, the prime mover is generally decoupled in a conventional manner, namely through the use of a friction dutch disposed directly behind the electric motor. This embodiment of the decoupling device is described in German Patent Application DE 10 2007 043 016 A1, for example.
Planetary transmissions constructed coaxially with the electric motor need very little radial and axial installation space and generally achieve the required overall transmission ratio without problems through the use of two speed-changing stages. However, arranging a decoupling device in a manner similar to the conventional drive train with a friction clutch would considerably reduce the advantage of coaxial transmissions in terms of installation space.
Thus, British Patent GB 1 219 195, for example, discloses a transmission in which different transmission stages are achieved through the use of planetary stages. Here, the two planetary stages can be coupled or decoupled, wherein the coupling device is provided or formed between the two planet wheel stages, as a result of which the transmission requires a correspondingly long installation space in terms of its axial length.
Thus, European Patent Application EP 1 142 743 A2, for example, discloses a transmission in which individual gear stages can be coupled and decoupled within the transmission through the use of elements similar to sliding sleeves, wherein the corresponding transmission also has planetary stages in a particular section in order to achieve particular gear stages. However, the coupling devices shown here require a correspondingly large amount of installation space, as a result of which the transmission itself also requires a correspondingly large amount of installation space.
More favorable in terms of the required installation space are “in-line transmissions”, which can be flanged coaxially to the drive motor, in particular to the electric motor. Typically for electric motors, the motor output shaft is coaxial with the motor windings. The transmission is flanged to the motor in such a way that the motor output shaft is connected coaxially to the transmission input shaft. Here, the transmission has a speed-changing section, i.e. a transmission part which implements the functionality of “speed changing,” and a downstream differential section, i,e. a transmission part which implements the functionality of a “differential,” Both sections are preferably integrated into a housing. In this configuration, both differential output shafts are aligned coaxially with one another, with the input shaft and with the motor output shaft. Here, one of the differential output shafts passes through the transmission input shaft and the motor output shaft, in particular, wherein the two latter shafts are configured as hollow shafts. In this case, the speed-changing section of the transmission formed in this way has two planetary stages, namely an input stage and a bad stage, wherein the individual components of the input stage and of the bad stage, which are each configured as planetary stages, are now connected to one another in a specific way. In particular, the sun wheel of the input stage is operatively connected to the input shaft, wherein the bad stage has an annulus fixed in relation to the housing and the sun wheel thereof, i.e. the sun wheel of the bad stage, can be connected operatively to at least one planet wheel (or the planetary set) of the input stage through the use of a planet carrier and wherein at least one planet wheel of the bad stage (or the planetary set) can be connected operatively to the annulus of the input stage through the use of a planet carrier. The intention is now to further improve this “in-line transmission” embodied or described in this way, taking into account certain premises.